JPH07179777A - Color-memorizing microcapsule pigment varying color with temperature - Google Patents

Abstract

PURPOSE:To obtain a color-memorizing microcapsule pigment exhibiting a specific color-density/temperature curve and useful for paint, printing ink, etc., by encapsulating a homogeneous solution of an electron-donative color- developing organic compound, an electron-accepting compound and a specific aliphatic ketone in microcapsules. CONSTITUTION:This pigment is produced by micro-encapsulating a homogeneous solution containing (A) an electron-donative color-developing compound [e.g. 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide], (B) an electron- accepting compound (e.g. phenol and n-butyl p-hydroxybenzoate) and (C) a 10-22C aliphatic ketone (e.g. 4-decanone) to control the color-developing reaction of the components A and B as essential components. The color-density/ temperature curve of the pigment is characterized by the discoloration with a hysteresis width (DELTAH) of 8-30 deg.C, the development of reversible color change between colored state and extinct state and the capability to reversibly memorize the low-temperature color and the high-temperature color relative to the discoloration temperature in a normal temperature range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosensitive color-changing color-memory color microcapsule pigment. More specifically, it exhibits a large hysteresis characteristic due to a temperature change and exhibits a reversible discoloration of coloring-decoloring, and even after removing the application of heat or cold heat required for discoloration, any of the colored state and the decolored state The present invention relates to a thermosensitive color-changing, color-memory color microcapsule pigment that retains color in a normal temperature range in a reciprocal manner.

[0002]

2. Description of the Related Art The present applicant has previously proposed a thermosensitive color-changing color memory material of this type (Japanese Patent Publication No. 4-171).
No. 54). The temperature-sensitive color-changing color memory material has a conventional general-purpose reversible thermochromic material that changes its color before and after the color-change temperature as a boundary, and has only one specific state in the room temperature region before and after the color-change. I can't. That is, the other state is maintained while the heat or cold required to develop that state is applied, but returns to the state exhibited at room temperature when the heat or cold is no longer applied. On the other hand, both the color on the low temperature side and the color on the high temperature side of the discoloration temperature can be selectively retained in the normal temperature range even after removing the heat or cold heat required for the discoloration. , Which can be held in an alternating manner by applying heat or cold heat as necessary, temperature-sensitive recording materials, toys,
It is applied to various fields such as decoration and printing.

[0003]

By the way, this kind of color memory effect is specified by a compound selected from esters which control a color reaction, as disclosed in Japanese Patent Publication No. 4-17154. Since it is a thermochromic effect that can be expressed only in the system in which the compound of (1) is applied as a constituent component, the utilization of this type of thermochromic material is restricted,
The discovery of new effective compounds has been awaited. The present inventors further pursued a compound as a reaction medium that exhibits the above-mentioned color memory effect, increased the degree of freedom in selection of the reaction medium, and further, high density during color development and good color disappearance during color erasing. Due to the very high contrast, the present invention seeks to further increase the utilization of this type of thermosensitive color-changing color memory material.

[0004]

Means for Solving the Problems In the system in which a compound selected from fatty acid ketones having a total carbon number of 10 to 22 is applied as a reaction medium for a color reaction, the hysteresis width (ΔH) The present invention has been completed by discovering that it exhibits a large thermochromic property, exhibits an effective color memory effect, and can obtain a very high contrast due to a high density at the time of color development and good color fading at the time of color erasing. Let The present invention relates to (a) an electron-donating color-developing organic compound, (b) an electron-accepting compound, (c) a fat having a total carbon number of 10 to 22 for controlling the color reaction of (a) and (b). A color density-temperature curve showing a hysteresis width (ΔH) of 8 ° C to 30 ° C in which a homogenous compatible solution containing three components of compounds selected from the group ketones as essential components is encapsulated in a microcapsule and changes color. It requires a thermosensitive color-changing color memory microcapsule pigment.

The hysteresis characteristic in the color density-temperature curve of the thermosensitive color-changing color-memory microcapsule pigment of the present invention will be described below with reference to the graph of FIG. In FIG. 1, the vertical axis represents color density and the horizontal axis represents temperature. The change in color density due to the temperature change progresses along the arrow. Here, A is a point showing the density at the minimum temperature T ₄ (hereinafter referred to as the color development / decoloration branch temperature) at which the color is completely erased, and B
Is a point showing the density at the maximum temperature T ₃ (hereinafter referred to as the maximum holding temperature) at which the completely colored state can be maintained, and C is the minimum temperature T ₂ at which the completely decolored state can be maintained (hereinafter referred to as the minimum holding temperature). ) Is a point indicating the density, and D is a point indicating the density at the maximum temperature T ₁ (hereinafter, referred to as a perfect coloration temperature) at which the perfect coloration state is reached. At the temperature T _A , two phases of the colored state E point and the decolored state F point coexist. The temperature range in which the colored state and the decolored state coexist, including this temperature T _A , is the temperature range in which discoloration can be maintained, and the line segment EF
Is the measure of the contrast of discoloration, and the line segment E
The length of the line segment HG passing through the midpoint of F is the temperature width indicating the degree of hysteresis (hereinafter referred to as hysteresis width ΔH), and the larger this ΔH value, the easier it is to maintain each state before and after discoloration. . In the experiments conducted by the present inventors, the ΔH value that can be retained before and after practical discoloration is in the range of 8 ° C to 30 ° C. In addition, in the above, the temperature at which the two phases of the colored state and the decolored state are substantially retained and is practically used, that is, the temperature range between T ₃ and T ₂ including T _A is 2 ° C. or more and 30 ° C. or more. The range below ℃ is effective.

Further, since the length of the line segment EF serves as a measure of contrast, the color densities in the E state and the F state are represented by lightness values V _E and V _F , and the degree of contrast is ΔV (V
_F- V _E ). The brightness value at the time of emitting and erasing is 0 for perfect black and 10 for perfect white in an achromatic array.
, The luminosity value of the Munsell color chart system divided so that the difference in sensation of brightness becomes equal sensation, and the luminosity value of the chromatic color is the aluminance value of the achromatic color whose sensation of the brightness of the chromatic color is equal to this. Indicates. That is, the smaller the lightness value is, the closer it is to black, and the larger the lightness value is, the closer it is to white. Therefore, the index for measuring the density at the time of color development and the degree of residual color at the time of erasing The brightness difference (ΔV) can be used as an index for contrast. Therefore, the density difference between chromatic colors having the same hue can be expressed by the difference in lightness value regardless of the type of hue.

The proportions of the three components (a), (b) and (c) in the present invention depend on the concentration, the color change temperature, the color change form and the type of each component, but generally desired characteristics are obtained. The obtained component ratio is such that the component (b) is 0.
1 to 50, preferably 0.5 to 20, component (c) 1 to 8
00, preferably 5 to 200 (the above proportions are all parts by weight). Further, each component may be a mixture of two or more kinds, and as long as the function is not impaired, an antioxidant, an ultraviolet absorber, a singlet oxygen quencher, an infrared absorber,
A dissolution aid, etc. can be added. Further, by adding a general pigment (non-thermochromic), it is possible to impart a color change from colored [1] to colored [2].

Specific examples of the compounds (a), (b) and (c) will be shown below. The component (a) of the present invention, that is, the electron-donating color-developing organic compound, includes conventionally known diphenylmethanephthalides, fluoranes,
Examples include diphenylmethane azaphthalide, indolyl phthalide, phenyl indolyl phthalide, phenyl indolyl azaphthalide, and styrylquinoline. Examples of these compounds are shown below. 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide,
3- (4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) phthalide, 3-
(4-Diethylamino-2-ethoxyphenyl) -3-
(1-Ethyl-2-methylindol-3-yl) -4
-Azaphthalide, 1,3-dimethyl-6-diethylaminofluorane, 2-chloro-3-methyl-6-dimethylaminofluorane, 3-dibutylamino-6-methyl-
7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-
6-methyl-7-xylidinofluorane, 2- (2-chloroanilino) -6-dibutylaminofluorane, 3,
6-dimethoxyfluorane, 3,6-di-n-butoxyfluorane, 1,2-benz-6-diethylaminofluorane, 1,2-benz-6-dibutylaminofluorane, 1,2-benz-6 -Ethylisoamylaminofluorane, 2-methyl-6- (Np-tolyl-N-ethylamino) fluorane, 2- (N-phenyl-N-methylamino) -6- (Np-tolyl-N -Ethylamino) fluorane, 2- (3'-trifluoromethylanilino) -6-diethylaminofluorane, 3-chloro-
6-cyclohexylaminofluorane, 2-methyl-6
-Cyclohexylaminofluorane, 3-methoxy-4
-Dodecoxystyrylquinoline and the like.

The electron-accepting compound of component (b) is
There are a compound group having an active proton, a pseudo-acidic compound group [a compound group which is not an acid but acts as an acid in the composition to develop the component (a)], a compound group having electron holes. Examples of the compound having an active proton include compounds having a phenolic hydroxyl group, from monophenols to polyphenols, and further, as a substituent thereof, an alkyl group, an aryl group, an acyl group, an alkoxycarbonyl group, a carboxy group and an ester thereof. Alternatively, examples thereof include those having an amide group, a halogen group and the like, and bis type and tris type phenols and the like, phenol-aldehyde condensation resins and the like. Further, it may be a metal salt of the compound having a phenolic hydroxyl group.

Specific examples will be given below. Phenol, o-
Cresol, tert-butylcatechol, nonylphenol, n-octylphenol, n-dodecylphenol, n-stearylphenol, p-chlorophenol, p-bromophenol, o-phenylphenol, n-butyl p-hydroxybenzoate, p-hydroxy. N-octyl benzoate, resorcin, dodecyl gallate, 2,2-bis (4-hydroxyphenyl) propane, 4,4-dihydroxydiphenyl sulfone, 1,1
-Bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxy-3-methylphenyl) propane,
Bis (4-hydroxyphenyl) sulfide, 1-phenyl-1,1-bis (4-hydroxyphenyl) ethane, 1,1-bis (4-hydroxyphenyl) -3-methylbutane, 1,1-bis (4- Hydroxyphenyl)
-2-methylpropane, 1,1-bis (4-hydroxyphenyl) n-hexane, 1,1-bis (4-hydroxyphenyl) n-heptane, 1,1-bis (4-hydroxyphenyl) n-octane , 1,1-bis (4-hydroxyphenyl) n-nonane, 1,1-bis (4-hydroxyphenyl) n-decane, 1,1-bis (4-hydroxyphenyl) n-dodecane, 2,2- Bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) ethyl propionate, 2,2-bis (4-hydroxyphenyl) -4-methylpentane,
2,2-bis (4-hydroxyphenyl) hexafluoropropane, 2,2-bis (4-hydroxyphenyl)
n-heptane, 2,2-bis (4-hydroxyphenyl) n-nonane, and the like. The compound having a phenolic hydroxyl group can develop the most effective thermochromic properties, but aromatic carboxylic acids and aliphatic carboxylic acids having 2 to 5 carbon atoms, carboxylic acid metal salts, acidic phosphoric acid esters and those It may be a compound selected from metal salts, 1,2,3-triazole and derivatives thereof.

Next, the total carbon number of the component (c) is 10 to 22.
Specific examples of the aliphatic ketones will be given below.
2-Decanone, 3-Decanone, 4-Decanone, 2-Undecanone, 3-Undecanone, 4-Undecanone, 5-
Undecanone, 6-Undecanone, 2-Dodecanone, 3
-Dodecanone, 4-Dodecanone, 5-Dodecanone, 2-
Tridecanone, 3-tridecanone, 2-tetradecanone, 2-pentadecanone, 8-pentadecanone, 2-hexadecanone, 3-hexadecanone, 9-heptadecane, 2-pentadecanone, 2-octadecanone, 2-nonadecanone, 10-nonadecanone, 2-eicosanone,
11-henei cosanone, 2-henei cosanone, 2-
Docosanone, etc. are mentioned. Although the above-mentioned aliphatic ketones are used as the component (c) of the present invention, other esters, alcohols, carboxylic acids, amides and the like can be added, if necessary, within a range that does not significantly change the hysteresis characteristics. In this case, the addition amount of the aliphatic ketone 5 of the present invention is
50 parts or less (parts by weight) with respect to 0 parts is preferable for effectively exhibiting the desired color memory effect.

The homogeneous compatible solution of the composition of the above-mentioned three essential components (a), (b) and (c) is encapsulated in a microcapsule by a known microencapsulation technique. Fine particles (0.
5 to 50 μm, preferably 1 to 30 μm), a characteristic having a larger ΔH value than in the non-fine particle state can be imparted,
By being protected by the capsule membrane wall, acidic substances,
Contact with a chemically active substance such as a basic substance or a peroxide, or other solvent components does not impair the function thereof, and can also maintain the heat stability. The microencapsulation techniques that can be used include interfacial polymerization and in Sit
u polymerization method, submerged curing coating method, phase separation method from aqueous solution, phase separation method from organic solvent, melt dispersion cooling method, air suspension coating method, spray drying method, etc. To be selected. Incidentally, the surface of the microcapsules may be provided with a secondary resin film to impart durability, or the surface characteristics may be modified for practical use according to the purpose.

[0013]

By blending a compound selected from the above aliphatic ketones as a reaction medium of a color reaction by electron transfer in the present invention, thermochromic characteristics exhibiting a large hysteresis width (ΔH) with respect to a color density-temperature curve are exhibited. In addition, due to the high density at the time of coloring and the goodness of color disappearance at the time of erasing,
By functioning as a color-changing composition having a very high contrast (ΔV) and by forming the composition into a fine particle form by encapsulating the composition in a fine capsule, ΔH effective for expressing a color memory effect is 8 Hysteresis characteristics of ℃ to 30 ℃ can be expressed. Although the theoretical elucidation of the above-mentioned action is still insufficient, with respect to high contrast,
It is speculated that the aliphatic ketone compound of the present invention has less total carbon number and higher polarizability under the same melting point than the ester compound. The thermochromic behavior is repeatedly reproduced as seen in the measured data of thermochromic characteristics of the examples described below.

[0014]

EXAMPLES Examples 1 to 10 Examples of the present invention will be shown below, but the present invention is not limited thereto. The method for producing the temperature-sensitive color-changing color-memory microcapsule pigment, the method for measuring the hysteresis characteristic of the microcapsule pigment according to the temperature change, and the method for measuring the contrast in each example will be described below. The parts in the following formulation examples are parts by weight.

Method for producing temperature-sensitive color-changing color-memory color microcapsule pigment (a) 3-dibutylamino-6-methyl-7-anilinofluorane 3.0 as an electron-donating color-forming organic compound
Part, as a (b) phenol compound, 2,2-bis (4
-Hydroxyphenyl) propane (8.0 parts) and (C) the aliphatic ketone compound of the present invention (50.0 parts)
Dissolved by heating at 20 ° C to form a homogenous solution, Epon 82
8 [Epoxy resin manufactured by Yuka Shell Epoxy Co., Ltd.] 10
Part and 10 parts of methyl ethyl ketone were mixed and then added dropwise to 100 parts of 10% gelatin aqueous solution,
Stir to make fine droplets. Separately, a solution prepared by dissolving 5 parts of a curing agent, Epicure U [made by Yuka Shell Epoxy Co., Ltd., amine adduct of epoxy resin] in 45 parts of water was gradually added to the stirring solution. The liquid temperature was maintained at 80 ° C. and stirring was continued for about 5 hours to obtain a microcapsule stock solution. By centrifuging the stock solution, a thermosensitive color-changing color-memory microcapsule pigment having a water content of about 40% by weight and changing from black to colorless was obtained.

Method for Measuring Hysteresis Properties 40 parts of the thermosensitive color-changing color-memory microcapsule pigment obtained as described above, 50 parts of ethylene-vinyl acetate emulsion, 1 part of defoaming agent, 1 part of leveling agent, 8 parts of water Using a 180-mesh screen plate, the ink uniformly dispersed in the area is solid-printed on white fine paper with a brightness value of 9.2 and completely dried. A printed matter of memory microcapsule pigment was obtained. The obtained printed matter was heated and cooled by the following method, and the color change behavior was plotted on a graph. A color difference meter [TC-3
600 type color difference meter, manufactured by Tokyo Denshoku Co., Ltd.], and attached at a predetermined location at a temperature range of 50 ° C. and 10 ° C./mi
The print was heated and cooled at a rate of n. For example, Example 1
In the case of, the measurement starting temperature is -30 ° C, and the temperature is 10 ° C / m.
Heating at a rate of in to 20 ° C, followed by 10 ° C / mi
It was cooled again to -30 ° C at a rate of n. Plot the brightness value displayed on the color difference meter at each temperature on the graph,
The color change curves illustrated in FIG. 1 are created, and T ₁ , T ₂ , T ₃ , T
₄ , T _H (temperature at the midpoint of color density in the coloring process), T
_G (temperature at the midpoint of color density in the erasing process), and ΔH
Each value of (line segment HG) was obtained.

Method of Measuring Contrast At the time of measuring the hysteresis characteristic, for example, in the case of Example 1, the lightness value V _E at −30 ° C. is used as a color difference meter [TC-3.
600 type color difference meter, manufactured by Tokyo Denshoku Co., Ltd.], and then the brightness value V _F at 20 ° C. was similarly read, and the contrast ΔV was calculated as V _F −V _E. The component (c) applied to the production of the thermosensitive color-changing color memory microcapsule pigment, and T ₁ , T ₂ , T ₃ , T ₄ , T _H (the temperature at the midpoint of the color density in the coloring process), T _G (temperature at the midpoint of color density in the erasing process), and ΔH (line segment HG)
Table 1 shows each value of.

[Table 1]

Example 11 Preparation of temperature-sensitive color-changing color-memory color microcapsule pigment (a) As an electron-donating color-forming organic compound, 3.0 parts of 6- (ethylisobutylamino) benzo α-fluorane,
(B) As a phenol compound, three components consisting of 8.0 parts of 2,2-bis (4-hydroxyphenyl) propane and 50.0 parts of (iii) 8-pentadecanone were dissolved by heating at 120 ° C. to obtain a homogeneous phase. After forming a solution and mixing it with a mixed solution of 10 parts of Epon 828 [Epoxy resin manufactured by Yuka Shell Epoxy Co., Ltd.] and 10 parts of methyl ethyl ketone, this was mixed with 1 part.
The mixture is added dropwise to 100 parts of 0% gelatin aqueous solution and stirred so as to form fine droplets. Separately prepared 5 parts of curing agent Epicure U
A solution prepared by dissolving 45 parts of water in [Okaka Shell Epoxy Co., Ltd., amine adduct of epoxy resin] was gradually added to the stirring solution to maintain the liquid temperature at 80 ° C. for about 5 minutes. Stirring was continued for a while to obtain a microcapsule stock solution. By centrifuging the stock solution, a thermosensitive color-changing color-memory microcapsule pigment having a water content of about 40% by weight and changing from pink to colorless was obtained.

Example 12 Preparation of thermosensitive color-changing color memory microcapsule pigment (a) 3- (4-) as an electron donating color-forming organic compound
Diethylamino-2-ethoxyphenyl) -3- (1-
1.5 parts of ethyl-2-methylindolyl-3-yl) -4-azoazophthalide, 8.0 parts of 2,2-bis (4-hydroxyphenyl) propane as a (b) phenol compound, (c) 8- A thermosensitive color-changing color-memory microcapsule pigment that changes from blue to colorless was obtained by the same method as in Example 11 from 3 components consisting of 50.0 parts of pentadecanone.

40 parts of the obtained temperature-sensitive color-changing, color-memory color microcapsule pigments were blended and prepared in the same manner as in Examples 1 to 10, respectively, using a 180 mesh screen plate on white fine paper having a lightness value of 9.2. Screen printing was performed, and the color change characteristics and lightness value of the printed matter were read using the color difference meter used in Examples 1 to 10, and the contrast ΔV was calculated as V _F −V _E. Each value is shown in Table 2.

[Table 2]

Comparative Examples 1 to 5 (a) 3-dibutylamino-6-methyl-7-anilinofluorane 3.0 as an electron-donating color-forming organic compound
Parts, 8.0 parts of 2,2-bis (4′-hydroxyphenyl) propane as a (b) phenol compound,
(C) Known ester compound having color memory 50.
Three components consisting of 0 parts were heated and dissolved at 120 ° C. to form a homogeneous phase compatible solution, and Epon 828 [Okaka Shell Epoxy Co., Ltd.
Production, Epoxy Resin] 10 parts by weight and a mixed solution of 10 parts of methyl ethyl ketone are mixed, and this is added dropwise to 100 parts of 10% gelatin aqueous solution and stirred so as to form fine droplets. Separately, a solution prepared by dissolving 5 parts of a curing agent, Epicure U [made by Yuka Shell Epoxy Co., Ltd., amine adduct of epoxy resin] in 45 parts of water was gradually added to the stirring solution. The liquid temperature was maintained at 80 ° C. and stirring was continued for about 5 hours to obtain a microcapsule stock solution. By centrifuging the stock solution, a thermosensitive color-changing color-memory microcapsule pigment having a water content of about 40% by weight that changes from black to colorless can be obtained, and in the same manner as in Examples 1 to 10. , Read its color change characteristics and brightness value, and set contrast ΔV to V
It was calculated as _F -V _E. Table 3 shows each value.

[Table 3]

Comparative Example 6 (a) As an electron-donating color-developing organic compound, 3.0 parts of 6- (ethylisobutylamino) benzo α-fluorane,
(B) As a phenol compound, 8.0 parts of 2,2-bis (4-hydroxyphenyl) propane and 50.0 parts of (c) n-heptyl stearate were microencapsulated by the same method, and pink to colorless. A microcapsule pigment having a temperature-sensing color-changing and color-storing color memory was obtained. Comparative Example 7 (a) As the electron-donating color-developing organic compound, 3- (4-
Diethylamino-2-ethoxyphenyl) -3- (1-
1.5 parts of ethyl-2-methylindolyl-3-yl) -4-azoazophthalide, 8.0 parts of 2,2-bis (4-hydroxyphenyl) propane as a (b) phenol compound, (c) stearic acid 50.0 parts of n-heptyl was microencapsulated by the same method to obtain a thermochromic color memory pigment having a color change from blue to colorless.

The color-changing characteristics and lightness values of the temperature-sensitive color-changing color-memory color microcapsule pigments obtained in Comparative Examples 6 and 7 were read in the same manner as in Examples 11 and 12.
The contrast ΔV was calculated as V _F −V _E. Table 4 shows each value.

[Table 4]

Application Example 1 (a) 3-dibutylamino-6-methyl-7-anilinofluorane, (b) 1,1-bis (4-hydroxyphenyl) -3-methylbutane, (c) 8-pentadecanone The three-component homogeneous compatible solution of (3) was microencapsulated by an epoxy resin / amine interfacial polymerization method to obtain an average particle size of 10
A microcapsule pigment having a color-changing and color-storing color memory of μm was obtained. The obtained thermosensitive color-changing color-memory microcapsule pigment has a black-colorless reversible thermochromic property (T ₁ : 7 ° C.,
T _4: having a 39 ° C.). An ink dispersed in an ethylene-vinyl acetate emulsion containing the thermosensitive color-changing color memory microcapsule pigment is printed on the surface of white fine paper using a screen plate (180 mesh) to obtain a thermosensitive color-changing recording paper. It was made. In the normal state, the recording paper is made to appear black, and becomes white when heated at 40 ° C. or higher.
This state is maintained at room temperature of about 25 ° C. Next about 7 ℃
When cooled below, it became black, and this state was maintained at room temperature. Either the black state or the white state of the recording paper could be retained alternately at room temperature. A heating pen (55
White handwriting was visible when writing at (° C). On the other hand, when writing on the recording paper in a white state with a cold pen (0 ° C.), black handwriting was revealed. This state was kept at the room temperature.

Application Example 2 (a) 3-dibutylamino-6-methyl-7-anilinofluorane, (b) 1,1-bis (4-hydroxyphenyl) -3-methylbutane, (c) 2-pentadecanone The three-component homogeneous compatible solution of (3) was microencapsulated by an epoxy resin / amine interfacial polymerization method to obtain an average particle size of 10
A microcapsule pigment having a color-changing and color-storing color memory of μm was obtained. The obtained thermosensitive color-changing color-memory microcapsule pigment has a black-colorless reversible thermochromic property (T ₁ : 8 ° C.,
T _4: having a 39 ° C.). 40 parts of the obtained thermosensitive color-changing color memory microcapsule pigment was uniformly dispersed in 60 parts of a colorless and transparent water-based screen ink vehicle containing an acrylic acid emulsion as a main component, and a 109 mesh screen plate was used. Printing was performed on a printed material in which a polka dot pattern was drawn on white fine paper with bright chromatic colors of pink, blue, and yellow to obtain a temperature-sensitive color-changing color memory memorable printed matter. In the normal state, the printed matter is black, and the colorful polka dot pattern drawn on the background cannot be seen at all.
Although it was completely hidden by the black color, the black color disappeared and a bright polka dot pattern of pink, blue and yellow appeared by heating at 40 ° C. or higher. This state is kept at room temperature of about 25 ° C, and then when cooled to about 8 ° C or less, it becomes black again, and the bright polka dots of pink, blue, and yellow are completely hidden, and it is possible to see. lost. Either the black state or the chromatic color state of the printed matter can be retained alternately in the normal temperature range, and when the recording paper in the black state at room temperature is written with a heating pen (55 ° C.), The colorful and vivid handwriting was visible. On the other hand, when the printed matter in the state of a bright chromatic polka dot pattern was written with a cold pen (0 ° C.), black handwriting was revealed. This state was kept at the room temperature.

[0026]

The thermosensitive color-changing color-memory microcapsule pigment of the present invention has a color density-temperature curve of 8 ° C to 30 ° C.
It shows a hysteresis width (ΔH) of ℃ and causes reversible discoloration between color development and decoloration, and can store and retain both the color on the low temperature side and the color on the high temperature side in alternation at room temperature, which is necessary. By applying heat or cold heat accordingly, it is possible to reversibly reproduce one of the colors and effectively develop the characteristic of being able to retain the memory. Furthermore, high density at the time of coloring and color disappearance at the time of erasing It is possible to express a very high contrast due to its goodness. The thermosensitive color-changing color memory microcapsule pigment of the present invention can be applied to various coatings or printed materials as a paint or a printing ink, or can be melt-blended with a thermoplastic resin, wax or the like to have various forms. It is applied as a shaped object.

[Brief description of drawings]

FIG. 1 is a graph illustrating a hysteresis characteristic in a color density-temperature curve of a thermosensitive color-changing color memory microcapsule pigment of the present invention.

[Explanation of symbols]

T ₁ Full color temperature T ₂ Minimum holding temperature T ₃ Maximum holding temperature T ₄ Coloring and erasing branch temperature

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Claims (1)

[Claims] 1. (a) an electron-donating color-forming organic compound,
(B) An electron-accepting compound, and (c) three components of a compound selected from aliphatic ketones having a total carbon number of 10 to 22 for controlling the color reaction of (a) and (b), as essential components. A thermosensitive color-changing color-memory microcapsule pigment, which is obtained by encapsulating a homogenous compatible solution in a microcapsule and exhibits a hysteresis width (ΔH) of 8 ° C. to 30 ° C. with respect to a color density-temperature curve.